Plasma-based synthesis of multicomponent preform material for high-performance optical fibers

Laser active fibers with excellent optical performance such as low spectral attenuation, high beam quality and high power output require essentially an extremely homogenous distribution of laser active rare earth dopants without any clustering within the silica matrix of the core material. Fiber core materials fabricated using the well-established rare earth doping processes REPUSIL and MCVD encounter physical limitations in terms of dopant homogeneity and concentration levels. The newly developed plasma-based synthesis aims at overcoming those limitations, utilizing a microwave plasma jet at atmospheric pressure and liquid based organic precursor solutions for deposition of preform material. First results on one single multicomponent doping step incorporating laser active (Yb), RE solubility enhancing (Al) and refractive index decreasing species (F) into a silica host matrix will be presented. Initial deposition experiments and material sample analysis by exemplary EPMA and RAMAN spectroscopy indicate superior homogeneity of radial dopant distribution without any clustering.